Heat sink with protrusions on multiple sides thereof and apparatus using the same

ABSTRACT

Examples of a thermal management unit and an electronic apparatus utilizing the thermal management unit are described. In one aspect, the thermal management unit includes a heat sink. The heat sink includes a base portion, a first protrusion structure and a second protrusion structure. The base portion has a first side and a second side opposite the first side. The first protrusion structure protrudes from the first side of the base portion, and includes multiple fins. The second protrusion structure protrudes from the second side of the base portion, and includes multiple ribs. The heat sink may be made of silicon.

CROSS REFERENCE TO RELATED PATENT APPLICATION

The present disclosure is part of a Continuation application of U.S.patent application Ser. No. 14/507,806, filed on 6 Oct. 2014 andclaiming the priority benefit of provisional application U.S. PatentApplication No. 61/950,075, filed on 8 Mar. 2014. The aforementionedapplications are incorporated by reference in their entirety.

TECHNICAL FIELD

The present disclosure generally relates to the field of transfer ofthermal energy and, more particularly, to thermal management in anelectronic apparatus.

BACKGROUND

Unless otherwise indicated herein, the approaches described in thissection are not prior art to the claims in this application and are notadmitted to be prior art by inclusion in this section.

Compact heat-generating devices, such as integrated-circuits (includingmicroprocessors, graphics chips, memory chips, radio frequency (RF)chips, networking communication chips, microwave chips, navigationchips, etc.), laser diodes, light-emitting diodes (LEDs),vertical-cavity surface emitting lasers (VCSELs) and the like, generatethermal energy, or heat, when in operation. Compact heat-generatingdevices may function as, for example, sensors or application-specific IC(ASIC) drivers in a telecom router, cellular phone tower, datacommunications server or mainframe computers. Regardless of which typeof heat-generating device the case may be, heat generated by a compactheat-generating device needs to be removed or dissipated from thecompact heat-generating device in order to achieve optimum performanceof the compact heat-generating device by keeping its temperature withina safe operating range. With the form factor of compact heat-generatingdevices and the applications they are implemented in becoming eversmaller (e.g., the processor in a smartphone, a tablet computer or anotebook computer) and thus resulting in high heat density, it isimperative to effectively dissipate the high-density heat generated inan area of a small footprint to ensure safe and optimum operation ofcompact heat-generating devices operating under such conditions.

As compact heat-generating devices such as microprocessors, graphicschips, memory chips, etc. are typically mounted on a printed circuitboard (PCB) inside an electronic apparatus (e.g., a portable device),the PCB itself often acts as a heat sink and/or heat spreader since atleast part of the heat generated by a heat-generating device mounted ona PCB can be transferred from the heat-generating device to the PCB,e.g., by conduction through the direct contact(s) between theheat-generating device and the PCB. However, when there are more than onheat-generating devices mounted on the same PCB, have the PCB acting asa heat sink and/or heat spreader is not ideal as heat absorbed by thePCB from one heat-generating device tends to lower the thermal gradientin the PCB, thus lowering the amount of heat transferred to the PCB fromanother heat-generating device that is also mounted on the PCB. Worse,it may be possible that heat transferred from one heat-generating deviceis transferred to another heat-generating device through the PCB. Inother words, when multiple heat-generating devices are mounted on thesame PCB, thermal coupling between/among two or more of the multipleheat-generating devices through the PCB may occur, thus negativelyimpacting heat transfer away from one or more of the heat-generatingdevices to result in degradation in the performance and shortening oflifetime of the affected heat-generating devices.

SUMMARY

Various embodiments of a heat sink for thermal management in anelectronic apparatus are provided. Embodiments of the heat sink of thepresent disclosure have fins on more than one side of the heat sink.

In one aspect, a thermal management unit may include a heat sink thatincludes a base portion, a first protrusion structure and a secondprotrusion structure. The base portion may have a first side and asecond side opposite the first side. The first protrusion structure mayprotrude from the first side of the base portion, and may include aplurality of fins. The second protrusion structure may protrude from thesecond side of the base portion, and may include a plurality of ribs.

In some embodiments, the fins may extend along a first direction on thefirst side of the base portion, and the ribs may extend along the firstdirection on the second side of the base portion.

In some embodiments, the fins may extend along a first direction on thefirst side of the base portion, and the ribs may extend along a seconddirection on the second side of the base portion, where the firstdirection and second direction are orthogonal to one another.

In some embodiments, each of the fins may respectively include a baseconnected to the base portion and a tip opposite the base thereof. Asurface facing an adjacent fin and connecting the tip and the base of afin of the plurality of fins may be approximately 90° with respect to aplane defined by the first side of the base portion.

In some embodiments, each of the fins may respectively include a baseconnected to the base portion and a tip opposite the base thereof. Asurface facing an adjacent fin and connecting the tip and the base of afin of the plurality of fins may be greater than 90° with respect to aplane defined by the first side of the base portion.

In some embodiments, each of the ribs may respectively include a baseconnected to the base portion and a tip opposite the base thereof. Asurface facing an adjacent rib and connecting the tip and the base of arib of the plurality of ribs may be approximately 90° with respect to aplane defined by the second side of the base portion.

In some embodiments, each of the ribs may respectively include a baseconnected to the base portion and a tip opposite the base thereof. Asurface facing an adjacent rib and connecting the tip and the base of arib of the plurality of ribs may be greater than 90° with respect to aplane defined by the second side of the base portion.

In some embodiments, an amount of protrusion of a fin of the pluralityof fins measured from the first side of the base portion and an amountof protrusion of a rib of the plurality of ribs measured from the secondside of the base portion may be different.

In some embodiments, an amount of protrusion of a first rib of theplurality of ribs measured from the second side of the base portion andan amount of protrusion of a second rib of the plurality of ribsmeasured from the second side of the base portion may be different.

In some embodiments, the heat sink may be made of silicon.

In some embodiments, the thermal management unit may further include aphase-change material and a container. The phase-change material may bein direct contact with at least a portion of the heat sink. Thecontainer may be coupled to the heat sink such that the phase-changematerial is contained in a space defined by the container and the heatsink.

In some embodiments, the phase-change material may include a salthydrate, an ionic liquid, paraffin, fatty acid, ester, anorganic-organic compound, an organic-inorganic compound, or aninorganic-inorganic compound.

In some embodiments, the container may be made of silicon, plastic,ceramic or metal.

In some embodiments, the container may include a pouch that is coupledto the heat sink by heat and pressure, solder, pressure-sensitiveadhesive, or epoxy.

In some embodiments, the container may include a pouch that includes ametallic foil.

In some embodiments, the container may include a pouch that includes analuminum foil having surface areas coated with biaxially-orientedpolyethylene terephthalate (BoPET).

In some embodiments, the container may be coupled to the first side ofthe heat sink such that the fins of the heat sink are in direct contactwith the phase-change material.

In some embodiments, the container may be coupled to the second side ofthe heat sink such that the ribs of the heat sink are in direct contactwith the phase-change material.

In some embodiments, the thermal management unit may further include aheat-generating device coupled to the first side of the heat sink. Aside of the heat-generating device that faces the heat sink may beconfigured to interlockingly engage with the first protrusion structureof the heat sink.

In some embodiments, the thermal management unit may further include athermal paste, solder, or epoxy disposed between the heat-generatingdevice and the heat sink.

In another aspect, an electronic apparatus may include a main unit and athermal management unit. The main unit may include a substrate and atleast one integrated-circuit (IC) chip. The substrate may have a firstside and a second side opposite the first side. The at least one IC chipmay be disposed on the second side of the substrate. The thermalmanagement unit may be disposed on the first side of the substrate. Thethermal management unit may include a heat sink that includes a baseportion, a first protrusion structure and a second protrusion structure.The base portion may have a first side and a second side opposite thefirst side. The first protrusion structure may protrude from the firstside of the base portion, and may include a plurality of fins. Thesecond protrusion structure may protrude from the second side of thebase portion, and may include a plurality of ribs, the second protrusionstructure in direct contact with the first side of the substrate whenthe heat sink is disposed on the first side of the substrate such thatat least a portion of heat in the substrate is conducted to the heatsink through the second protrusion structure.

In some embodiments, the fins may extend along a first direction on thefirst side of the base portion, and the ribs may extend along the firstdirection on the second side of the base portion.

In some embodiments, the fins may extend along a first direction on thefirst side of the base portion, and the ribs may extend along a seconddirection on the second side of the base portion, where the firstdirection and second direction are orthogonal to one another.

In some embodiments, each of the fins may respectively include a baseconnected to the base portion and a tip opposite the base thereof. Asurface facing an adjacent fin and connecting the tip and the base of afin of the plurality of fins may be approximately 90° with respect to aplane defined by the first side of the base portion.

In some embodiments, each of the fins may respectively include a baseconnected to the base portion and a tip opposite the base thereof. Asurface facing an adjacent fin and connecting the tip and the base of afin of the plurality of fins may be greater than 90° with respect to aplane defined by the first side of the base portion.

In some embodiments, each of the ribs may respectively include a baseconnected to the base portion and a tip opposite the base thereof. Asurface facing an adjacent rib and connecting the tip and the base of arib of the plurality of ribs may be approximately 90° with respect to aplane defined by the second side of the base portion.

In some embodiments, each of the ribs may respectively include a baseconnected to the base portion and a tip opposite the base thereof. Asurface facing an adjacent rib and connecting the tip and the base of arib of the plurality of ribs may be greater than 90° with respect to aplane defined by the second side of the base portion.

In some embodiments, an amount of protrusion of a fin of the pluralityof fins measured from the first side of the base portion and an amountof protrusion of a rib of the plurality of ribs measured from the secondside of the base portion may be different.

In some embodiments, an amount of protrusion of a first rib of theplurality of ribs measured from the second side of the base portion andan amount of protrusion of a second rib of the plurality of ribsmeasured from the second side of the base portion may be different.

In some embodiments, the heat sink may be made of silicon.

In some embodiments, the electronic apparatus may further include athermal epoxy disposed between the heat sink and the substrate.

In some embodiments, the electronic apparatus may further include asolder disposed between the ribs of the heat sink and the first side ofthe substrate. The electronic apparatus may additionally include athermal epoxy or solder disposed in a space defined by the first side ofthe substrate and a gap between every two immediately adjacent ribs ofthe heat sink.

In some embodiments, the first side of the substrate may be at leastpartially metalized with a first metal layer, and at least one of theribs having a surface that faces the substrate may be metalized with asecond metal layer.

In some embodiments, the electronic apparatus may further include asolder disposed between the first side of the substrate and a surface ofeach of the ribs that faces the substrate such that the first metallayer and the second metal layer are bonded by the solder. Theelectronic apparatus may additionally include a thermal epoxy or solderdisposed in a space defined by the first side of the substrate and a gapbetween every two immediately adjacent ribs of the heat sink.

In some embodiments, the first side of the substrate may include apattern configured to interlockingly engage with the second protrusionstructure of the heat sink when the heat sink is disposed on the firstside of the substrate.

In some embodiments, the pattern may include a plurality of groovescorresponding to the ribs of the heat sink. The grooves may beconfigured to receive and be in direct contact with the ribs when theheat sink is disposed on the first side of the substrate.

In some embodiments, the substrate may include a multi-layered printedcircuit board (PCB) that includes a plurality of PCB layers and one ormore metal layers each of which sandwiched between two immediatelyadjacent PCB layers of the plurality of PCB layers.

In some embodiments, one or more of the PCB layers may be patterned tointerlockingly engage with the second protrusion structure of the heatsink.

In some embodiments, a surface of each of the one or more of the PCBlayers that are patterned to interlockingly engage with the secondprotrusion structure of the heat sink may define the first side of thesubstrate and may be metalized with a respective metal layer.

In some embodiments, the substrate may further include one or morethermal vias traversing a thickness of the substrate from the first sideof the substrate to the second side of the substrate.

In some embodiments, at least one of the one or more thermal vias maycorrespond to a respective one of the at least one IC chip and may beconfigured to conduct heat from the respective one of the at least oneIC chip in a direction from the second side of the substrate toward thefirst side of the substrate.

In some embodiments, the thermal management unit may further include aphase-change material and a container. The phase-change material may bein direct contact with at least a portion of the heat sink. Thecontainer may be coupled to the heat sink such that the phase-changematerial is contained in a space defined by the container and the heatsink.

In some embodiments, the phase-change material may include a salthydrate, an ionic liquid, paraffin, fatty acid, ester, anorganic-organic compound, an organic-inorganic compound, or aninorganic-inorganic compound.

In some embodiments, the container may be made of silicon, plastic,ceramic or metal.

In some embodiments, the container may include a silicon cover having ahollow therein.

In some embodiments, the container may include a pouch that is coupledto the heat sink by heat and pressure, solder, pressure-sensitiveadhesive, or epoxy.

In some embodiments, the container may include a pouch that includes ametallic foil.

In some embodiments, the container may include a pouch that includes analuminum foil having surface areas coated with BoPET.

In some embodiments, the container may be coupled to the first side ofthe heat sink such that the fins of the heat sink are in direct contactwith the phase-change material.

In some embodiments, the container may be coupled to the second side ofthe heat sink such that the ribs of the heat sink are in direct contactwith the phase-change material.

In some embodiments, the electronic apparatus may further include anenclosure enclosing the main unit and the thermal management unittherein. An inner side of the enclosure that faces the thermalmanagement unit may be configured to interlockingly engage with thefirst protrusion structure of the heat sink.

In some embodiments, the enclosure may be made of metal.

In some embodiments, the electronic apparatus may further include athermal paste, solder, or epoxy disposed between the enclosure and theheat sink.

The foregoing summary is illustrative only and is not intended to belimiting in any way. That is, the foregoing summary is provided tointroduce concepts relating to a heat sink for thermal management in anelectronic apparatus. Select embodiments of the novel and non-obvioustechnique are further described below in the detailed description. Thus,the foregoing summary is not intended to identify essential features ofthe claimed subject matter, nor is it intended for use in determiningthe scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the disclosure, and are incorporated in and constitutea part of the present disclosure. The drawings illustrate embodiments ofthe disclosure and, together with the description, serve to explain theprinciples of the disclosure. It is appreciable that the drawings arenot necessarily in scale as some components may be shown to be out ofproportion than the size in actual implementation in order to clearlyillustrate the concept of the present disclosure.

FIG. 1A is a perspective view of a heat sink in accordance with someembodiments of the present disclosure.

FIG. 1B is a cross-sectional view of the heat sink of FIG. 1A.

FIG. 2A is a perspective view of a heat sink in accordance with someembodiments of the present disclosure.

FIG. 2B is a cross-sectional view of the heat sink of FIG. 2A.

FIG. 3A is a perspective view of a heat sink in accordance with someembodiments of the present disclosure.

FIG. 3B is a cross-sectional view of the heat sink of FIG. 3A.

FIG. 4 is a side view of a thermal management assembly for an electronicapparatus and using a heat sink and a substrate in accordance with someembodiments of the present disclosure.

FIG. 5 is a side view of another thermal management assembly for anelectronic apparatus and using a heat sink and a substrate in accordancewith some embodiments of the present disclosure.

FIG. 6A is a top perspective view of a thermal management assembly foran electronic apparatus and using a heat sink and a substrate inaccordance with some embodiments of the present disclosure.

FIG. 6B is a bottom perspective view of the thermal management assemblyof FIG. 6A.

FIG. 7 is a cross-sectional view of a thermal management assembly for anelectronic apparatus and using a heat sink and a substrate in accordancewith some embodiments of the present disclosure.

FIG. 8 is a cross-sectional view of another thermal management assemblyfor an electronic apparatus and using a heat sink and a substrate inaccordance with some embodiments of the present disclosure.

FIG. 9 is a perspective view of a thermal management assembly for anelectronic apparatus and using a heat sink in accordance with someembodiments of the present disclosure.

FIG. 10 is a first cross-sectional view of the thermal managementassembly of FIG. 9, viewing from a first direction.

FIG. 11 is a second cross-sectional view of the thermal managementassembly of FIG. 9, viewing from a second direction that is orthogonalto the first direction.

FIG. 12 is a perspective view of a thermal management assembly of acompact heat-generating device mounted on a heat sink in accordance withsome embodiments of the present disclosure.

FIG. 13 is a perspective view of the heat sink of FIG. 12.

FIG. 14 is a perspective view of a thermal management assembly of acompact heat-generating device mounted on another heat sink inaccordance with some embodiments of the present disclosure.

FIG. 15 is a perspective view of the heat sink of FIG. 14.

FIG. 16A is a perspective view of a thermal management assembly for anelectronic apparatus and using a heat sink and a thermal reservoir inaccordance with some embodiments of the present disclosure.

FIG. 16B is a cross-sectional view of the thermal management assembly ofFIG. 16A.

FIG. 17A is a perspective view of another thermal management assemblyfor an electronic apparatus and using a heat sink and a thermalreservoir in accordance with some embodiments of the present disclosure.

FIG. 17B is a cross-sectional view of the thermal management assembly ofFIG. 17A.

FIG. 18A is a perspective view of yet another thermal managementassembly for an electronic apparatus and using a heat sink and a thermalreservoir in accordance with some embodiments of the present disclosure.

FIG. 18B is a cross-sectional view of the thermal management assembly ofFIG. 18A.

FIG. 19A is a perspective view of a part of an electronic apparatusutilizing a thermal management scheme in accordance with someembodiments of the present disclosure.

FIG. 19B is a cross-sectional view of the part of the electronicapparatus utilizing the thermal management scheme of FIG. 19A.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Overview

The present disclosure describes implementations of a heat sink forthermal management in an electronic apparatus. The heat sink inaccordance with the present disclosure may be made of silicon or metal.In one implementation, the heat sink may have protrusions, e.g., finsand ribs, protruding from two opposing sides of a base portion of theheat sink. This novel and non-obvious design is different fromconventional heat sinks in that conventional heat sinks are designed tobe mounted on a flat surface while the heat sink of the presentdisclosure is mounted on a PCB, or any other heat spreader, with groovesthat correspond to, receive and accommodate the protrusions on thebottom side of the heat sink. Protrusions on the bottom side of the heatsink increase the surface area for heat conduction between the PCB andthe heat sink to enhance transfer heat from the PCB or any other heatspreader. Additionally, compared to heat sinks with a flat bottom sidewith no protrusions thereon, protrusions on the bottom side of the heatsink contribute to improvement on thermal stress relief.

In a multiple-layer, or multi-layered, PCB, most of the layers in thePCB spread heat around in order to remove heat. When mounted on amulti-layered PCB, protrusions on the bottom side of the heat sink ofthe present disclosure can remove heat from any of the multiple layersof the PCB such that the heat sink enables isolation of thermal effectbetween/among the layers of the multi-layered PCB. In other words, theproposed thermal management scheme of the present disclosure can isolateheat around layers of the PCB to allow compact heat-generating devices(e.g., ICs) mounted on the multi-layered PCB to operate at a lowertemperature, thus enhancing the performance of the heat-generatingdevices.

In some implementations, a heat sink in accordance with the presentdisclosure has protrusions protruding from two opposing sides thereof inthat protrusions (e.g., fins) on one side of the heat sink run in afirst direction and protrusions (e.g., ribs) on the opposing side of theheat sink run in a second direction that is orthogonal, orperpendicular, to the first direction. This design increases stresstolerance for tensile or compressive forces within the structure of theheat sink, and thus making it feasible to manufacture large-size heatsinks with protrusions on two opposing sides thereof.

Illustrative Implementations

FIG. 1A is a perspective view of a heat sink 101 in accordance with someembodiments of the present disclosure. FIG. 1B is a cross-sectional viewof heat sink 101 along the line AA′.

Heat sink 101 may be implemented in a thermal management unit which willbe described below. As shown in FIGS. 1A and 1B, heat sink 101 includesa base portion, a first protrusion structure and a second protrusionstructure. The base portion may have a first side (e.g., the top side asshown in FIGS. 1A and 1B) and a second side (e.g., the bottom side asshown in FIGS. 1A and 1B) that is opposite the first side. The firstprotrusion structure protrudes from the first side of the base portion,and includes multiple fins 11. The second protrusion structure protrudesfrom the second side of the base portion, and includes multiple ribs 12.In some other embodiments, the first protrusion structure may includemultiple ribs and the second protrusion structure may include multiplefins. Alternatively, the first protrusion structure may include multiplefins and the second protrusion structure may include multiple fins.Still alternatively, the first protrusion structure may include multipleribs and the second protrusion structure may include multiple ribs.Thus, those skilled in the art would appreciate that, although the firstprotrusion structure includes fins 11 and the second protrusionstructure includes ribs 12 as illustrated in FIG. 1, the scope of thepresent disclosure is not limited thereto.

Heat sink 101 may additionally include protrusions from any of thesecondary sides, or edges, between the first side and the second side ofthe base portion. That is, heat sink 101 may include protrusions thatprotrude from the base portion of heat sink 101 in two or more differentdirections. For simplicity, heat sink 101 is illustrated to haveprotrusions on the first side and the second side of the base portionthereof. Thus, those skilled in the art would appreciate that, althoughheat sink 101 has first protrusion structure and second protrusionstructure protruding from the first side and the second side thereof asillustrated in FIG. 1, the scope of the present disclosure is notlimited thereto and may include additional protrusion structuresprotruding in different direction(s).

In the example shown in FIGS. 1A and 1B, fins 11 extend along a firstdirection on the first side of the base portion, and ribs 12 extendalong the first direction on the second side of the base portion. Thatis, fins 11 and ribs 12 extend along the same direction and thus areparallel to each other.

Each of the fins 11 respectively has a base connected to the baseportion of the heat sink 101. Each of the fins 11 also respectively hasa tip opposite the base thereof. In heat sink 101, a surface connectingthe tip and the base of a first fin that faces a second fin which isimmediately adjacent the first fin is approximately 90° with respect toa plane defined by the first side of the base portion. As shown in FIG.1B, the angle α1 is approximately 90°. This feature is applicable toeach of the fins 11 in heat sink 101. That is, each of the fins 11 ofheat sink 101 has one or two main surfaces facing its immediatelyadjacent fin, and the one or more main surfaces are substantiallyparallel to each other and are substantially perpendicular to the planedefined by the first side of the base portion. In other words, a widthof the base and a width of the tip of each of the fins 11 viewed in thedirection as shown in FIG. 1B are substantially equal. Put differently,each of the fins 11 has a generally rectangular profile in thecross-sectional view as shown in FIG. 1B.

Similarly, each of the ribs 12 respectively has a base connected to thebase portion of the heat sink 101. Each of the ribs 12 also respectivelyhas a tip opposite the base thereof. In heat sink 101, a surfaceconnecting the tip and the base of a first rib that faces a second ribwhich is immediately adjacent the first rib is approximately 90° withrespect to a plane defined by the second side of the base portion. Thisfeature is applicable to each of the ribs 12 in heat sink 101. That is,each of the ribs 12 of heat sink 101 has one or two main surfaces facingits immediately adjacent rib, and the one or more main surfaces aresubstantially parallel to each other and are substantially perpendicularto the plane defined by the second side of the base portion. In otherwords, a width of the base and a width of the tip of each of the ribs 12viewed in the direction as shown in FIG. 1B are substantially equal. Putdifferently, each of the ribs 12 has a generally rectangular profile inthe cross-sectional view as shown in FIG. 1B.

In some embodiments, an amount of protrusion of a fin of the fins 11measured from the first side of the base portion (e.g., height h1 asshown in FIG. 1B) and an amount of protrusion of a rib of the ribs 12measured from the second side of the base portion (e.g., height h2 asshown in FIG. 1B) are different. As shown in FIGS. 1A and 1B, the heightof fins 11 is greater than the height of ribs 12.

In some embodiments, an amount of protrusion of a first rib of the ribs12 measured from the second side of the base portion and an amount ofprotrusion of a second rib of ribs 12 measured from the second side ofthe base portion may be different. That is, ribs 12 may have the sameheight or different heights.

In some embodiments, heat sink 101 is made of silicon such as, forexample, single-crystal silicon. Alternatively, heat sink 101 is made ofmetal such as, for example, copper, aluminum or an alloy.

In the case that heat sink 101 is made of silicon, a silicon wafer maybe fabricated by etching or plasma-etching to create the firstprotrusion structure and the second protrusion structure on opposingsides of the silicon wafer. The size and pitches of fins 11 and ribs 12may be different. Ribs 12 are configured to attach to a heat source orheat spreader such as, for example, a PCB, metal heat-plate,heat-generating device, etc. so that heat is transferred from the heatsource or heat spreader to heat sink 101 through ribs 12. Fins 11 areconfigured to dissipate the heat into the surrounding (e.g., air).Accordingly, fins 11 have a height h1 greater than a height h2 of ribs12 to result in a total surface area of fins 11 to be much larger than atotal surface area of ribs 12. This is because fins 11 need to dissipateheat into the surrounding. The area ratio (h1/h2) of the height of fins11 to the height of ribs 12 is thus at least greater than 1 in order toallow heat sink 101 to dissipate heat through fins 11. Otherwise, theheat may be accumulated in ribs 12.

FIG. 2A is a perspective view of a heat sink 102 in accordance with someembodiments of the present disclosure. FIG. 2B is a cross-sectional viewof heat sink 102 along the line BB′.

Heat sink 102 may be implemented in a thermal management unit which willbe described below. As shown in FIGS. 2A and 2B, heat sink 102 includesa base portion, a first protrusion structure and a second protrusionstructure. The base portion may have a first side (e.g., the top side asshown in FIGS. 2A and 2B) and a second side (e.g., the bottom side asshown in FIGS. 2A and 2B) that is opposite the first side. The firstprotrusion structure protrudes from the first side of the base portion,and includes multiple fins 13. The second protrusion structure protrudesfrom the second side of the base portion, and includes multiple ribs 14.One main difference between heat sink 102 and heat sink 101 is that thefins 13 and ribs 14 of heat sink 102 have a tapered, or sloped,structure as described below. That is, fins 13 and ribs 14 of heat sink102 have tapered/sloped side walls. In some other embodiments, the firstprotrusion structure may include multiple ribs and the second protrusionstructure may include multiple fins. Alternatively, the first protrusionstructure may include multiple fins and the second protrusion structuremay include multiple fins. Still alternatively, the first protrusionstructure may include multiple ribs and the second protrusion structuremay include multiple ribs. Thus, those skilled in the art wouldappreciate that, although the first protrusion structure includes fins13 and the second protrusion structure includes ribs 14 as illustratedin FIG. 2, the scope of the present disclosure is not limited thereto.

Heat sink 102 may additionally include protrusions from any of thesecondary sides, or edges, between the first side and the second side ofthe base portion. That is, heat sink 102 may include protrusions thatprotrude from the base portion of heat sink 102 in two or more differentdirections. For simplicity, heat sink 102 is illustrated to haveprotrusions on the first side and the second side of the base portionthereof. Thus, those skilled in the art would appreciate that, althoughheat sink 102 has first protrusion structure and second protrusionstructure protruding from the first side and the second side thereof asillustrated in FIG. 2, the scope of the present disclosure is notlimited thereto and may include additional protrusion structuresprotruding in different direction(s).

In the example shown in FIGS. 2A and 2B, fins 13 extend along a firstdirection on the first side of the base portion, and ribs 14 extendalong the first direction on the second side of the base portion. Thatis, fins 13 and ribs 14 extend along the same direction and thus areparallel to each other.

Each of the fins 13 respectively has a base connected to the baseportion of the heat sink 102. Each of the fins 13 also respectively hasa tip opposite the base thereof. In heat sink 102, a surface connectingthe tip and the base of a first fin that faces a second fin which isimmediately adjacent the first fin is greater than 90° with respect to aplane defined by the first side of the base portion. As shown in FIG.2B, the angle α2 is greater than 90°. This feature is applicable to eachof the fins 13 in heat sink 102. That is, each of the fins 13 of heatsink 102 has one or two main surfaces facing its immediately adjacentfin, and the one or more main surfaces are not parallel to each otherand are sloped with respect to the plane defined by the first side ofthe base portion. In other words, a width of the base and a width of thetip of each of the fins 13 viewed in the direction as shown in FIG. 2Bare different (i.e., the width of the base is greater than the width ofthe tip). Put differently, each of the fins 13 has a generallytrapezoidal profile in the cross-sectional view as shown in FIG. 2B.

Similarly, each of the ribs 14 respectively has a base connected to thebase portion of the heat sink 102. Each of the ribs 14 also respectivelyhas a tip opposite the base thereof. In heat sink 102, a surfaceconnecting the tip and the base of a first rib that faces a second ribwhich is immediately adjacent the first rib is greater than 90° withrespect to a plane defined by the second side of the base portion. Asshown in FIG. 2B, the angle α3 is greater than 90°. This feature isapplicable to each of the ribs 14 in heat sink 102. That is, each of theribs 14 of heat sink 102 has one or two main surfaces facing itsimmediately adjacent rib, and the one or more main surfaces are notparallel to each other and are sloped with respect to the plane definedby the second side of the base portion. In other words, a width of thebase and a width of the tip of each of the ribs 14 viewed in thedirection as shown in FIG. 2B are different (i.e., the width of the baseis greater than the width of the tip). Put differently, each of the ribs14 has a generally trapezoidal profile in the cross-sectional view asshown in FIG. 2B.

In some embodiments, an amount of protrusion of a fin of the fins 13measured from the first side of the base portion and an amount ofprotrusion of a rib of the ribs 14 measured from the second side of thebase portion are different. As shown in FIGS. 2A and 2B, the height offins 13 is greater than the height of ribs 14.

In some embodiments, an amount of protrusion of a first rib of the ribs14 measured from the second side of the base portion and an amount ofprotrusion of a second rib of ribs 14 measured from the second side ofthe base portion may be different. That is, ribs 14 may have the sameheight or different heights.

In some embodiments, heat sink 102 is made of silicon such as, forexample, single-crystal silicon. Alternatively, heat sink 102 is made ofmetal such as, for example, copper, aluminum or an alloy.

In the case that heat sink 102 is made of silicon, a silicon wafer maybe fabricated by etching or plasma-etching to create the firstprotrusion structure and the second protrusion structure on opposingsides of the silicon wafer. The size and pitches of fins 13 and ribs 14may be different. Ribs 14 are configured to attach to a heat source orheat spreader such as, for example, a PCB, metal heat-plate,heat-generating device, etc. so that heat is transferred from the heatsource or heat spreader to heat sink 102 through ribs 14. Fins 13 areconfigured to dissipate the heat into the surrounding (e.g., air).Accordingly, fins 13 have a height greater than a height of ribs 14 toresult in a total surface area of fins 13 to be much larger than a totalsurface area of ribs 14. This is because fins 13 need to dissipate heatinto the surrounding. The area ratio of the height of fins 13 to theheight of ribs 14 is thus at least greater than 1 in order to allow heatsink 102 to dissipate heat through fins 13. Otherwise, the heat may beaccumulated in ribs 14.

FIG. 3A is a perspective view of a heat sink 103 in accordance with someembodiments of the present disclosure. FIG. 3B is a cross-sectional viewof heat sink 103 along the ling CC′.

Heat sink 103 may be implemented in a thermal management unit which willbe described below. As shown in FIGS. 3A and 3B, heat sink 103 includesa base portion, a first protrusion structure and a second protrusionstructure. The base portion may have a first side (e.g., the top side asshown in FIGS. 3A and 3B) and a second side (e.g., the bottom side asshown in FIGS. 3A and 3B) that is opposite the first side. The firstprotrusion structure protrudes from the first side of the base portion,and includes multiple fins 15. The second protrusion structure protrudesfrom the second side of the base portion, and includes multiple ribs 16.In some other embodiments, the first protrusion structure may includemultiple ribs and the second protrusion structure may include multiplefins. Alternatively, the first protrusion structure may include multiplefins and the second protrusion structure may include multiple fins.Still alternatively, the first protrusion structure may include multipleribs and the second protrusion structure may include multiple ribs.Thus, those skilled in the art would appreciate that, although the firstprotrusion structure includes fins 15 and the second protrusionstructure includes ribs 16 as illustrated in FIG. 3, the scope of thepresent disclosure is not limited thereto.

Heat sink 103 may additionally include protrusions from any of thesecondary sides, or edges, between the first side and the second side ofthe base portion. That is, heat sink 103 may include protrusions thatprotrude from the base portion of heat sink 103 in two or more differentdirections. For simplicity, heat sink 103 is illustrated to haveprotrusions on the first side and the second side of the base portionthereof. Thus, those skilled in the art would appreciate that, althoughheat sink 103 has first protrusion structure and second protrusionstructure protruding from the first side and the second side thereof asillustrated in FIG. 3, the scope of the present disclosure is notlimited thereto and may include additional protrusion structuresprotruding in different direction(s).

In the example shown in FIGS. 3A and 3B, fins 15 extend along a firstdirection on the first side of the base portion, and ribs 16 extendalong a second direction on the second side of the base portion. Thefirst direction and the second direction are different and may, forexample, be orthogonal to one another. As shown in FIGS. 3A and 3B, fins15 and ribs 16 extend along different, e.g., orthogonal, directions.This feature improves the strength of the structure of heat sink 103 tobetter withstand thermal stress or mechanical stress caused by solderingor epoxy bonding.

Each of the fins 15 respectively has a base connected to the baseportion of the heat sink 103. Each of the fins 15 also respectively hasa tip opposite the base thereof. In heat sink 103, a surface connectingthe tip and the base of a first fin that faces a second fin which isimmediately adjacent the first fin is approximately 90° with respect toa plane defined by the first side of the base portion. This feature isapplicable to each of the fins 15 in heat sink 103. That is, each of thefins 15 of heat sink 103 has one or two main surfaces facing itsimmediately adjacent fin, and the one or more main surfaces aresubstantially parallel to each other and are substantially perpendicularto the plane defined by the first side of the base portion. In otherwords, a width of the base and a width of the tip of each of the fins 15viewed in the direction as shown in FIG. 3B are substantially equal. Putdifferently, each of the fins 15 has a generally rectangular profile inthe cross-sectional view as shown in FIG. 3B.

Similarly, each of the ribs 16 respectively has a base connected to thebase portion of the heat sink 103. Each of the ribs 16 also respectivelyhas a tip opposite the base thereof. In heat sink 103, a surfaceconnecting the tip and the base of a first rib that faces a second ribwhich is immediately adjacent the first rib is approximately 90° withrespect to a plane defined by the second side of the base portion. Thisfeature is applicable to each of the ribs 16 in heat sink 103. That is,each of the ribs 16 of heat sink 103 has one or two main surfaces facingits immediately adjacent rib, and the one or more main surfaces aresubstantially parallel to each other and are substantially perpendicularto the plane defined by the second side of the base portion. In otherwords, a width of the base and a width of the tip of each of the ribs 16viewed in the direction as shown in FIG. 3B are substantially equal. Putdifferently, each of the ribs 16 has a generally rectangular profile inthe cross-sectional view as shown in FIG. 3B.

In some embodiments, an amount of protrusion of a fin of the fins 15measured from the first side of the base portion and an amount ofprotrusion of a rib of the ribs 16 measured from the second side of thebase portion are different. As shown in FIGS. 3A and 3B, the height offins 15 is greater than the height of ribs 16.

In some embodiments, an amount of protrusion of a first rib of the ribs16 measured from the second side of the base portion and an amount ofprotrusion of a second rib of ribs 16 measured from the second side ofthe base portion may be different. That is, ribs 16 may have the sameheight or different heights.

In some embodiments, heat sink 103 is made of silicon such as, forexample, single-crystal silicon. Alternatively, heat sink 103 is made ofmetal such as, for example, copper, aluminum or an alloy.

In the case that heat sink 103 is made of silicon, a silicon wafer maybe fabricated by etching or plasma-etching to create the firstprotrusion structure and the second protrusion structure on opposingsides of the silicon wafer. The size and pitches of fins 15 and ribs 16may be different. Ribs 16 are configured to attach to a heat source orheat spreader such as, for example, a PCB, metal heat-plate,heat-generating device, etc. so that heat is transferred from the heatsource or heat spreader to heat sink 103 through ribs 16. Fins 15 areconfigured to dissipate the heat into the surrounding (e.g., air).Accordingly, fins 15 have a height greater than a height of ribs 16 toresult in a total surface area of fins 15 to be much larger than a totalsurface area of ribs 16. This is because fins 15 need to dissipate heatinto the surrounding. The area ratio of the height of fins 15 to theheight of ribs 16 is thus at least greater than 1 in order to allow heatsink 103 to dissipate heat through fins 15. Otherwise, the heat may beaccumulated in ribs 16.

It is noteworthy that, although not illustrated in FIGS. 1-3, any, someor all of the fins and ribs of the heat sink of the present disclosuremay have a shape different from those illustrated in FIGS. 1-3. Forexample, a heat sink in accordance with the present disclosure may havepin fins each of which having a generally cylindrical shape withstraight side walls or a spike-like shape with tapered or slopedsidewalls. The same applies to the ribs. In other words, a heat sink inaccordance with the present disclosure may have protrusions on multiplesides thereof, and the protrusions, whether fins or ribs, may have anyconceivable shape that can be manufactured. For example, the fins may bestraight fins, tapered or sloped fins, flared fins, pin fins, etc.

FIG. 4 is a side view of a thermal management assembly 5001 for anelectronic apparatus and using heat sink 101 and a substrate 21 inaccordance with some embodiments of the present disclosure. Althoughheat sink 101 is illustrated in the example shown in FIG. 4, in otherembodiments, heat sink 102 or heat sink 103 may be utilized in place ofheat sink 101.

Thermal management assembly 5001 includes a main unit and a thermalmanagement unit. The main unit includes the substrate 21 and at leastone heat-generating device 22. Substrate 21 may be a PCB. The at leastone heat-generating device 22 may include one or more compact devicessuch as, for example, integrated-circuits (including microprocessors,graphics chips, memory chips, RF chips, networking communication chips,microwave chips, navigation chips, etc.), laser diodes, LEDs and VCSELs.Substrate 21 has a first side (e.g., top side as shown in FIG. 4) and asecond side (e.g., bottom side as shown in FIG. 4) that is opposite thefirst side. Each of the at least one heat-generating device 22 isdisposed on the second side (e.g., bottom side) of substrate 21.Substrate 21 is generally electrically insulating and thermallyconductive.

Thermal management unit of thermal management assembly 5001 includes oneor more heat sinks each of which includes protrusions (e.g., fins and/orribs) on multiple sides thereof. The one or more heat sinks of thermalmanagement assembly 5001 may include, for example, heat sink 101, heatsink 102 and/or heat sink 103. Thus, in the interest of brevity,detailed description of the heat sink of thermal management unit is notrepeated. Those skilled in the art would appreciate that, although heatsink 101 is illustrated in FIG. 4, the scope of the present disclosureis not limited thereto. Further, for simplicity, one heat sink and oneheat-generating device are illustrated in FIG. 4 and described below inreference to FIG. 4, although the technique of the present disclosurealso applies to scenarios in which there are multiple heat sinks and/ormultiple heat-generating devices disposed on substrate 21.

As shown in FIG. 4, heat sink 101 is disposed, attached, or otherwisemounted on the first side (e.g., top side) of substrate 21. Preferably,heat sink 101 is disposed at a location on the first side of substrate21 opposite the location on the second side of substrate 21 at which theat least one heat-generating device 22 is disposed. Heat sink 101 may bebonded to substrate 21 with medium 25, e.g., at the bottom side of theribs 12 and base portion of heat sink 101 as shown in FIG. 4. The use ofmedium 25 creates a heat transfer path of low thermal resistance betweensubstrate 21 and heat sink 101. This maximizes heat transfer fromsubstrate 21 to heat sink 101. Medium 25 may be, for example, thermalepoxy or thermal grease. It is perceived that most of the heat generatedby the at least one heat-generating device 22 will flow throughsubstrate 21 and transfer to ribs 12 of heat sink 101, while some amountof heat will flow through medium 25 and transfer to fins 11 and baseportion of heat sink 101. Fins 11 will radiate the heat into thesurrounding, e.g., air. An illustrative pattern of heat dissipation 26is shown in FIG. 4 as it may be naturally radiated and/or convected tothe air by forced-air from a fan or another means.

FIG. 5 is a side view of a thermal management assembly 5002 for anelectronic apparatus and using heat sink 101 and substrate 21 inaccordance with some embodiments of the present disclosure. Althoughheat sink 101 is illustrated in the example shown in FIG. 5, in otherembodiments, heat sink 102 or heat sink 103 may be utilized in place ofheat sink 101.

Thermal management assembly 5002 includes a main unit and a thermalmanagement unit. The main unit includes the substrate 21 and at leastone heat-generating device 22. Substrate 21 may be a PCB. The at leastone heat-generating device 22 may include one or more compact devicessuch as, for example, integrated-circuits (including microprocessors,graphics chips, memory chips, RF chips, networking communication chips,microwave chips, navigation chips, etc.), laser diodes, LEDs and VCSELs.Substrate 21 has a first side (e.g., top side as shown in FIG. 5) and asecond side (e.g., bottom side as shown in FIG. 5) that is opposite thefirst side. Each of the at least one heat-generating device 22 isdisposed on the second side (e.g., bottom side) of substrate 21.Substrate 21 is generally electrically insulating and thermallyconductive.

Thermal management unit of thermal management assembly 5002 includes oneor more heat sinks each of which includes protrusions (e.g., fins and/orribs) on multiple sides thereof. The one or more heat sinks of thermalmanagement assembly 5002 may include, for example, heat sink 101, heatsink 102 and/or heat sink 103. Thus, in the interest of brevity,detailed description of the heat sink of thermal management unit is notrepeated. Those skilled in the art would appreciate that, although heatsink 101 is illustrated in FIG. 5, the scope of the present disclosureis not limited thereto. Further, for simplicity, one heat sink and oneheat-generating device are illustrated in FIG. 5 and described below inreference to FIG. 5, although the technique of the present disclosurealso applies to scenarios in which there are multiple heat sinks and/ormultiple heat-generating devices disposed on substrate 21.

As shown in FIG. 5, heat sink 101 is disposed, attached, or otherwisemounted on the first side (e.g., top side) of substrate 21. Preferably,heat sink 101 is disposed at a location on the first side of substrate21 opposite the location on the second side of substrate 21 at which theat least one heat-generating device 22 is disposed.

At least a portion of the first side of substrate 21 is metalized with ametal layer 27. For example, the portion of the first side of substrate21 that corresponds to heat sink 101 may be coated with metal layer 27.Alternatively, the entire or a majority of the first side of substrate21 may be coated with metal layer 27. Correspondingly, at least aportion of the bottom side of heat sink 101, which faces the first sideof substrate 21 as shown in FIG. 5, is metalized with a metal layer. Asshown in FIG. 5, the bottom surface of the tip of each of ribs 12 andthe bottom surface of the base portion of heat sink 101 are coated witha metal layer 29. Metal layer 27 and metal layer 29 may be coated onsubstrate 21 and heat sink 101, respectively, by metal deposition ormetal-spray. Medium 28 is used to bond metal layer 27 on substrate 21 tothe portion of metal 29 that is on the bottom surface of the tip of eachof ribs 12. Medium 24 is used to bond metal layer 27 on substrate 21 tothe portion of metal 29 that is on the bottom surface of the baseportion of heat sink 101. Medium 24 also fills in a space defined by thefirst side of substrate 21 and a gap between every two immediatelyadjacent ribs 12 of heat sink 101. The use of medium 28 and medium 24creates a heat transfer path of low thermal resistance between substrate21 and heat sink 101. This maximizes heat transfer from substrate 21 toheat sink 101. Medium 28 may be solder and medium 24 may be thermalepoxy or solder. It is perceived that most of the heat generated by theat least one heat-generating device 22 will flow through substrate 21and transfer to ribs 12 of heat sink 101, while some amount of heat willflow through medium 24 and transfer to fins 11 and base portion of heatsink 101. Fins 11 will radiate the heat into the surrounding, e.g., air.An illustrative pattern of heat dissipation 26 is shown in FIG. 5 as itmay be naturally radiated and/or convected to the air by forced-air froma fan or another means.

FIG. 6A is a top perspective view of a thermal management assembly 5003for an electronic apparatus and using heat sink 101 and a substrate 201in accordance with some embodiments of the present disclosure. FIG. 6Bis a bottom perspective view of thermal management assembly 5003 of FIG.6A.

Thermal management assembly 5003 includes a main unit and a thermalmanagement unit. The main unit includes the substrate 201 and at leastone heat-generating device (e.g., a first heat-generating device 48 anda second heat-generating device 49 are shown as an example). Substrate201 may be a PCB. The at least one heat-generating device may includeone or more compact devices such as, for example, integrated-circuits(including microprocessors, graphics chips, memory chips, RF chips,networking communication chips, microwave chips, navigation chips,etc.), laser diodes, LEDs and VCSELs. Substrate 201 has a first side(e.g., top side as shown in FIGS. 6A and 6B) and a second side (e.g.,bottom side as shown in FIGS. 6A and 6B) that is opposite the firstside. Each of the at least one heat-generating device is disposed on thesecond side (e.g., bottom side) of substrate 201. Substrate 201 isthermally conductive.

Thermal management unit of thermal management assembly 5003 includes oneor more heat sinks each of which includes protrusions (e.g., fins and/orribs) on multiple sides thereof. The one or more heat sinks of thermalmanagement assembly 5003 may include, for example, heat sink 101, heatsink 102 and/or heat sink 103. Thus, in the interest of brevity,detailed description of the heat sink of thermal management unit is notrepeated. Those skilled in the art would appreciate that, although heatsink 101 is illustrated in FIGS. 6A and 6B, the scope of the presentdisclosure is not limited thereto. Further, for simplicity, one heatsink and one heat-generating device are illustrated in FIGS. 6A/6B anddescribed below in reference to FIGS. 6A and 6B, although the techniqueof the present disclosure also applies to scenarios in which there aremultiple heat sinks and/or fewer or more heat-generating devicesdisposed on substrate 201.

As shown in FIGS. 6A and 6B, substrate 201 includes multiple layers.Substrate 201 may be, for example, a multi-layered PCB. That is,substrate 201 may be a multi-layered PCB with multiple layers therein.That is, substrate 201 may be a multi-layered structure having layers ofelectrically-conductive layers (e.g., one or more layers of metal) andelectrically-insulating layers (e.g., one or more layers of insulator)interlaced or otherwise sandwiched in an alternating fashion. In theexample shown in FIGS. 6A and 6B, substrate 201 has threeelectrically-insulating layers. Those skilled in the art wouldappreciate that, although substrate 201 is illustrated to have threeelectrically-insulating layers in FIGS. 6A and 6B, the scope of thepresent disclosure is not limited thereto. For example, substrate 201may have fewer (e.g., two) or more (e.g., four or more) layers than whatis illustrated in FIGS. 6A and 6B.

As shown in FIGS. 6A and 6B, substrate 201 includes a first layer 35(e.g., the top layer) on which heat sink 101 is disposed, a second layer36 (e.g., the middle layer) and a third layer 37 (e.g., the bottomlayer) on which at least one heat-generating device, such as a firstheat-generating device 48 and a second heat-generating device 49, isdisposed. Second layer 36 sandwiched between first layer 35 and thirdlayer 37. First layer 35 of substrate 201 may be patterned to receive,accommodate, fit or otherwise engage with heat sink 101. For example,the side of first layer 35 that constitute the first side (e.g., topside) of substrate 201 may include grooves, indentations and/orthrough-holes that are shaped and contoured to accommodate ribs 12 andthe bottom side of the base portion of heat sink 101. This allowssubstrate 201 to interlockingly receive, accommodate, fit or otherwiseengage with heat sink 101. In other words, first layer 35 of substrate201 is patterned so that substrate 201 and heat sink 101 interlock witheach other when heat sink 101 is disposed on the first side of substrate201. This feature increases the total surface area in contact betweensubstrate 201 and heat sink 101 to maximize heat transfer from substrate201 to heat sink 101. This feature also increases the structuralstrength of heat sink 201 as well as mechanical integrity of thermalmanagement assembly 5003.

FIG. 7 is a cross-sectional view of thermal management assembly 5003. Asshown in FIG. 7, a metal layer 41 (e.g., copper layer) is coated onsolder joints between the bottom surface of the tip of each rib 12 andsubstrate 201 (e.g., first layer 35 and/or second layer 36, where ribs12 come in contact with substrate 201). The bottom surface of the tip ofeach rib 12 may be metalized and bonded to substrate 201 (e.g., firstlayer 35 and/or second layer 36) by medium 42. For example, medium 42may be solder when ribs 12 are soldered to substrate 201, and medium 42may be thermal epoxy when ribs 12 are epoxied to substrate 201.Likewise, as shown in FIG. 7, first heat-generating device 48 and secondheat-generating device 49 may be bonded to the second side of substrate201 (e.g., third layer 37) by medium 44. Medium 44 may be, for example,solder when first heat-generating device 48 and second heat-generatingdevice 49 are soldered onto substrate 201. The side of each of firstheat-generating device 48 and second heat-generating device 49 thatfaces substrate 201 may be metalized with a metal layer 45.

Substrate 201 includes one or more thermal vias (e.g., thermal vias 31,32 and 33 as shown in FIG. 7) that traverse a thickness of thesubstrate. Some of the thermal vias (e.g., thermal vias 31 and 32)traverse through the entire thickness of substrate 201, i.e., from thefirst side of substrate 201 to the second side of substrate 201, whileother thermal vias (e.g., thermal via 33) traverse through a portion ofbut not the entire thickness of substrate 201. In some embodiments, atleast one of the one or more thermal vias may correspond to a respectiveone of the at least one heat-generating device and may be configured toconduct heat from the respective one of the at least one heat-generatingdevice in a direction from the second side of substrate 201 toward thefirst side of substrate 201. Each of the one or more thermal viasincludes a thermally-conductive material. The thermally-conductivematerial may be metal such as, for example, copper. Although threethermal vias (i.e., thermal vias 31, 32 and 33) are illustrated in FIG.7, in actual implementations substrate 201 may include fewer or morethermal vias. Therefore, the scope of thermal management assembly 5003in accordance with the present disclosure is not limited to what isillustrated in FIG. 7.

As shown in FIG. 7, first layer 35 of substrate 201 is patterned withthrough-holes to accommodate, and thus interlock with, ribs 12 of heatsink 101. In the illustrated example, as first layer 35 of substrate 201has through-holes, the metalized bottom surface of the tip of each rib12 is bonded to second layer 36 of substrate 201. The surface of secondlayer 36 facing heat sink 101, e.g., the portion of the top surface ofsecond layer 36 in contact with ribs 12, may be metalized with a metallayer 43. Accordingly, second layer 36 can directly dissipate heat intoheat sink 101 without going through the thermal vias (e.g., thermal vias31, 32). The interlock between ribs 12 of heat sink 101 and first layer35 of substrate 201 provides more surface area for paths of heattransfer via conduction from substrate 201 to heat sink 101. Thisfeature increases the rate of heat transfer as well as improvesstructural strength of heat sink 101.

As thermal vias 31 and 32 are aligned with first heat-generating device48 and second heat-generating device 49, respectively, heat generated byfirst heat-generating device 48 and second heat-generating device 49 canbe transferred to heat sink 101 through thermal vias 31 and 32.Moreover, heat absorbed by substrate 201 and trapped between secondlayer 36 and third layer 37 can be transferred to heat sink 101 throughthermal via 33. This feature enables efficient and effective heattransfer from first heat-generating device 48 and second heat-generatingdevice 49 to heat sink 101, and from substrate 201 to heat sink 101.

FIG. 8 is a cross-sectional view of a thermal management assembly 5004for an electronic apparatus and using a heat sink 104 and a substrate202 in accordance with some embodiments of the present disclosure.

Thermal management assembly 5004 includes a main unit and a thermalmanagement unit. The main unit includes the substrate 202 and at leastone heat-generating device (e.g., a first heat-generating device 72, asecond heat-generating device 73 and a third heat-generating device 74are shown as an example). Substrate 202 may be a PCB. The at least oneheat-generating device may include one or more compact devices such as,for example, integrated-circuits (including microprocessors, graphicschips, memory chips, RF chips, networking communication chips, microwavechips, navigation chips, etc.), laser diodes, LEDs and VCSELs. Substrate202 has a first side (e.g., top side as shown in FIG. 8) and a secondside (e.g., bottom side as shown in FIG. 8) that is opposite the firstside. Each of the at least one heat-generating device is disposed on thesecond side (e.g., bottom side) of substrate 202. Substrate 202 isthermally conductive.

Thermal management unit of thermal management assembly 5004 includes oneor more heat sinks each of which includes protrusions (e.g., fins and/orribs) on multiple sides thereof. The one or more heat sinks of thermalmanagement assembly 5004 may include, for example, heat sink 101, heatsink 102, heat sink 103 and/or heat sink 104. In the example shown inFIG. 8, heat sink 104 is utilized. In the interest of brevity, detaileddescription of features of heat sink 104 similar to those of heat sink101/102/103 are not repeated. While heat sink 104 has fins 11 a on thefirst side (e.g., top side as shown in FIG. 8) that may have the sameheight, heat sink has short ribs 12 a, medium ribs 12 b and long ribs 12c on the second side (e.g., bottom side as shown in FIG. 8). Fins 11 amay have straight or sloped side walls. Ribs 12 a/12 b/12 c may havestraight or sloped side walls. In the example shown in FIG. 8, fins 11 aand ribs 12 a/12 b/12 c have straight side walls.

Those skilled in the art would appreciate that, although heat sink 104is illustrated in FIG. 8, the scope of the present disclosure is notlimited thereto. Further, for simplicity, one heat sink and threeheat-generating devices are illustrated in FIG. 8 and described below inreference to FIG. 8, although the technique of the present disclosurealso applies to scenarios in which there are multiple heat sinks and/orfewer or more heat-generating devices disposed on substrate 202.

As shown in FIG. 8, substrate 202 includes multiple layers. Substrate202 may be, for example, a multi-layered PCB. That is, substrate 202 maybe a multi-layered PCB with multiple layers therein. That is, substrate202 may be a multi-layered structure having layers ofelectrically-conductive layers (e.g., one or more layers of metal) andelectrically-insulating layers (e.g., one or more layers of insulator)interlaced or otherwise sandwiched in an alternating fashion. In theexample shown in FIG. 8, substrate 202 has three electrically-insulatinglayers. Those skilled in the art would appreciate that, althoughsubstrate 201 is illustrated to have three electrically-insulatinglayers in FIG. 8, the scope of the present disclosure is not limitedthereto. For example, substrate 202 may have fewer (e.g., two) or more(e.g., four or more) layers than what is illustrated in FIG. 8.

As shown in FIG. 8, substrate 202 includes a first layer 75 (e.g., thetop layer) on which heat sink 104 is disposed, a second layer 76 (e.g.,the middle layer) and a third layer 77 (e.g., the bottom layer) on whichat least one heat-generating device, such as first heat-generatingdevice 72, second heat-generating device 73 and third heat-generatingdevice 74, is/are disposed. Second layer 76 is sandwiched between firstlayer 75 and third layer 77. First layer 75, second layer 76 and thirdlayer 77 of substrate 202 may be patterned to receive, accommodate, fitor otherwise engage with heat sink 104. For example, the side of firstlayer 75, second layer 76 and third layer 77 that face toward heat sink104 (e.g., top side) may include grooves, indentations and/orthrough-holes that are shaped and contoured to accommodate ribs 12 a/12b/12 c and the bottom side of the base portion of heat sink 104. Thisallows substrate 202 to interlockingly receive, accommodate, fit orotherwise engage with heat sink 104. In other words, first layer 75,second layer 76 and third layer 77 of substrate 202 are respectivelypatterned so that substrate 202 and heat sink 104 interlock with eachother when heat sink 104 is disposed on the first side of substrate 202.This feature increases the total surface area in contact betweensubstrate 202 and heat sink 104 to maximize heat transfer from substrate202 to heat sink 104. This feature also increases the structuralstrength of heat sink 104 as well as mechanical integrity of thermalmanagement assembly 5004.

As shown in FIG. 8, a metal layer 65 (e.g., copper layer) is coated onsolder joints between the bottom surface of heat sink 104 between ribs12 and substrate 202 (e.g., first layer 35 and/or second layer 36, whereribs 12 a/12 b/12 c come in contact with substrate 202). The bottomsurface of the tip of each rib 12 a/12 b/12 c may be metalized andbonded to substrate 202 (e.g., first layer 75, second layer 76 and/orthird layer 77) by medium 62. For example, medium 62 may be solder whenribs 12 a/12 b/12 c are soldered to substrate 202, and medium 62 may bethermal epoxy when ribs 12 a/12 b/12 c are epoxied to substrate 202.Likewise, as shown in FIG. 8, first heat-generating device 72, secondheat-generating device 73 and third heat-generating device 74 may bebonded to the second side of substrate 202 (e.g., third layer 77) bymedium 64. Medium 64 may be, for example, solder when firstheat-generating device 72, second heat-generating device 73 and thirdheat-generating device 74 are soldered onto substrate 202. The side ofeach of first heat-generating device 72, second heat-generating device73 and third heat-generating device 74 that faces substrate 202 may bemetalized with a metal layer 68. At least a portion of the second sideof substrate 202, e.g., the portion of the second side that bonds withfirst heat-generating device 72, second heat-generating device 73 andthird heat-generating device 74, may be coated with a metal layer 66.

Substrate 202 includes one or more thermal vias (e.g., thermal vias 50,51 and 53 as shown in FIG. 8) that traverse a thickness of thesubstrate. Some of the thermal vias (e.g., thermal via 53) traversethrough the entire thickness of substrate 202, i.e., from the first sideof substrate 202 to the second side of substrate 202, while otherthermal vias (e.g., thermal vias 50 and 51) traverse through a portionof but not the entire thickness of substrate 202. In some embodiments,at least one of the one or more thermal vias may correspond to arespective one of the at least one heat-generating device and may beconfigured to conduct heat from the respective one of the at least oneheat-generating device in a direction from the second side of substrate202 toward the first side of substrate 202. Each of the one or morethermal vias includes a thermally-conductive material. Thethermally-conductive material may be metal such as, for example, copper.Although three thermal vias (i.e., thermal vias 50, 51 and 53) areillustrated in FIG. 8, in actual implementations substrate 202 mayinclude fewer or more thermal vias. Therefore, the scope of thermalmanagement assembly 5004 in accordance with the present disclosure isnot limited to what is illustrated in FIG. 8.

As shown in FIG. 8, first layer 75 of substrate 202 is patterned withthrough-holes to accommodate, and thus interlock with, ribs 12 of heatsink 104. In the illustrated example, as first layer 75 of substrate 202has through-holes, the metalized bottom surface of the tip of each rib12 a is bonded to second layer 76 of substrate 202. The surface ofsecond layer 76 facing heat sink 104, e.g., the portion of the topsurface of second layer 76 in contact with ribs 12 a, may be metalizedwith a metal layer. Accordingly, second layer 76 can directly dissipateheat into heat sink 104 without going through the thermal vias (e.g.,thermal vias 51, 53). The interlock between ribs 12 a/12 b/12 c of heatsink 104 and first layer 75, second layer 76 and third layer 77 ofsubstrate 202 provides more surface area for paths of heat transfer viaconduction from substrate 202 to heat sink 104. This feature increasesthe rate of heat transfer as well as improves structural strength ofheat sink 104.

As thermal vias 51 and 53 are aligned with second heat-generating device73 and third heat-generating device 74, respectively, heat generated bysecond heat-generating device 73 and third heat-generating device 74 canbe transferred to heat sink 104 through thermal vias 51 and 53.Moreover, heat absorbed by substrate 202 and trapped between secondlayer 76 and third layer 77 can be transferred to heat sink 104 throughthermal via 50. This feature enables efficient and effective heattransfer from second heat-generating device 73 and third heat-generatingdevice 74 to heat sink 104, and from substrate 202 to heat sink 104.

Thermal management assembly 5004 of FIG. 8 differs from thermalmanagement assembly 5003 of FIG. 7 mainly due to ribs 12 a/12 b/12 chaving different heights as measured from the second side of heat sink104. As shown in FIG. 8, ribs 12 a have a height h3, ribs 12 b have aheight h4, and ribs 12 c have a height h5. Thus, ribs 12 a/12 b/12 cextend to and are bonded to (e.g., by soldering) to different layers ofsubstrate 202. For example, ribs 12 a are soldered to a metal layer 62at the top side of second layer 76 and other solder joints to removeheat from the metal layer between first layer 75 and second layer 76.Ribs 12 b are soldered to a metal layer 63 at the top side of thirdlayer 77 and other solder joints to remove heat from the metal layerbetween second layer 76 and third layer 77. As shown in FIG. 8, a rib 12c extends or traverses the entire thickness of substrate 202 to directlyconnect to first heat-generating device 72 through metal layer 66. Inother words, ribs 12 a/12 b/12 c, having different heights h3, h4 andh5, can directly connect to any metallization of the multiple layers ofsubstrate 202 to effectively transfer heat into heat sink 104 todissipate the heat into the surrounding, e.g., air. This feature allowsthermal management assembly 5004 to isolate heat from the variousheat-generating devices and to spread the heat around the layers ofsubstrate 202. The heights h3/h4/h5 of ribs 12 a/12 b/12 c are relatedto the thickness of first layer 75, second layer 76 and third layer 77,respectively. Thermal vias 50, 51 and 53 are also used to transfer heatthat is trapped in any layer of the multi-layered substrate 202.

FIG. 9 is a perspective view of a thermal management assembly 5005 foran electronic apparatus and using a heat sink 105 in accordance withsome embodiments of the present disclosure. FIG. 10 is a firstcross-sectional view of thermal management assembly 5005 of FIG. 9 alongline EE. FIG. 11 is a second cross-sectional view of thermal managementassembly 5005 of FIG. 9 along line FF on the second side (e.g., bottomside) of substrate 202. Substrate 202 is thermally.

Thermal management assembly 5005 includes a main unit and a thermalmanagement unit. The main unit includes the substrate 81 and at leastone heat-generating device (e.g., a heat-generating device 82 is shownas an example). Substrate 81 may be a PCB. The at least oneheat-generating device may include one or more compact devices such as,for example, integrated-circuits (including microprocessors, graphicschips, memory chips, RF chips, networking communication chips, microwavechips, navigation chips, etc.), laser diodes, LEDs and VCSELs. Substrate81 has a first side (e.g., top side as shown in FIGS. 9-11) and a secondside (e.g., bottom side as shown in FIGS. 9-11) that is opposite thefirst side.

Thermal management unit of thermal management assembly 5005 includes oneor more heat sinks each of which includes protrusions (e.g., fins and/orribs) on multiple sides thereof. The one or more heat sinks of thermalmanagement assembly 5005 may include, for example, heat sink 105. In theexample shown in FIGS. 9-11, heat sink 105 is utilized. Heat sink 105includes fins 11 b on the first side (e.g., top side) of heat sink 105and ribs 12 d on the second side (e.g., bottom side) of heat sink 105.Heat sink 105 is similar to heat sink 103 in that fins 11 b extend in afirst direction and ribs 12 d extend in a second direction that isdifferent from, e.g., orthogonal, to the first direction. In the exampleshown in FIGS. 9-11, fins 11 b and ribs 12 d extend in orthogonaldirections. In other embodiments, fins 11 b and ribs 12 b may extend inthe same direction. Fins 11 b may have straight or sloped side walls.Ribs 12 d may have straight or sloped side walls. In the example shownin FIGS. 9-11, fins 11 b and ribs 12 d have straight side walls.

As shown in FIGS. 9-11, heat sink 105 is mounted on heat-generatingdevice 82 and heat-generating device 82 is mounted on substrate 81.Heat-generating device 82 is bonded to and sandwiched between heat sink105 and substrate 81. In some embodiments, heat-generating device 82 maybe a ball-bumped IC chip that is soldered to substrate 81, which may bea PCB, and heat sink 105 may be bonded to heat-generating device 82,which is a ball-bumped IC chip. The bonding may utilize a thermal epoxyor metal solder. In the case of metal solder bonding, at least a portionof the second side (e.g., bottom side) of heat sink 105 is metalized.

FIG. 12 is a perspective view of a thermal management assembly 5011 ofheat-generating device 82 mounted on heat sink 105 in accordance withsome embodiments of the present disclosure. FIG. 13 is a perspectiveview of heat sink 105.

As shown in FIGS. 12 and 13, heat-generating device 82 is mounted on thesecond side (e.g., bottom side) of heat sink 105. Other than ribs 12 d,the second side of heat sink 105 also includes a mounting pad 98 thatprotrudes from the base portion of heat sink 105. Mounting pad 98 has aheight that may be substantially the same as the height of ribs 12 d.When heat-generating device 82 is disposed on the second side of heatsink 105, heat-generating device 82 may be disposed on mounting pad 98,as shown in FIG. 12. Mounting pad 98 may be constructed using chemicaletch in a silicon micro-electro-mechanical systems (MEMS) processperformed on single-crystal silicon.

FIG. 14 is a perspective view of a thermal management assembly 5012 ofheat-generating device 82 mounted on a heat sink 106 in accordance withsome embodiments of the present disclosure. FIG. 15 is a perspectiveview of heat sink 106 of FIG. 14.

Heat sink 106 has fins 11 c on the first side and ribs 12 e on thesecond side thereof. Heat sink 106 is similar to heat sink 105 in thatfins 11 c extend in a first direction and ribs 12 e extend in a seconddirection that is different from, e.g., orthogonal, to the firstdirection. In the example shown in FIGS. 14 and 15, fins 11 c and ribs12 e extend in orthogonal directions. In other embodiments, fins 11 cand ribs 12 e may extend in the same direction. Fins 11 c may havestraight or sloped side walls. Ribs 12 e may have straight or slopedside walls. In the example shown in FIGS. 14 and 15, fins 11 c and ribs12 e have straight side walls.

Heat sink 106 differs from heat sink 105 in that, instead of a mountingpad 98 as in the case of heat sink 105, heat sink 106 includes a recess99 on the second side thereof. Heat-generating device 82 is received inrecess 99 when mounted on heat sink 106. Heat-generating device 82 maybe bonded to recess 99 of heat sink 106 by solder or thermal epoxy. Inthe case of solder, at least a portion of the second side of heat sink106 (e.g., recess 99) and the side of heat-generating device 82 thatmates with recess 99 are metalized for soldering.

FIG. 16A is a perspective view of a thermal management assembly 5013 foran electronic apparatus and using heat sink 101 and a thermal reservoirin accordance with some embodiments of the present disclosure. FIG. 16Bis a cross-sectional view of thermal management assembly 5013 of FIG.16A along line GG.

Although heat sink 101 is illustrated in FIGS. 16A and 16B, thoseskilled in the art would appreciate that the scope of the presentdisclosure is not limited thereto. For example, other heat sinks such asheat sink 102, heat sink 103, heat sink 104, heat sink 105 or heat sink106 may be utilized in thermal management assembly 5013. Forillustrative purposes heat sink 101 is shown in the example of FIGS. 16Aand 16B.

Thermal reservoir includes a phase-change material 203 and a container202. Phase-change material 203 is contained in a space defined bycontainer 202 and heat sink 101. Phase-change material 203 may include asalt hydrate, an ionic liquid, paraffin, fatty acid, ester, anorganic-organic compound, an organic-inorganic compound, or aninorganic-inorganic compound. Container 202 may be made of silicon,plastic, ceramic or metal. In the example shown in FIGS. 16A and 16B,container 202 is a pouch. The pouch may be coupled to heat sink 101 byheat and pressure, solder, pressure-sensitive adhesive, or epoxy. Thepouch may be a metallic foil. In some embodiments, container 202 may bea pouch which may include an aluminum foil having surface areas coatedwith biaxially-oriented polyethylene terephthalate (BoPET). As shown inFIGS. 16A and 16B, container 202 is coupled to the first side of heatsink 101 such that fins 11 of heat sink 101 are in direct contact withphase-change material 203. Container 202, as a pouch, may be heat sealed(e.g., at heat seals 231 a and 231 d as shown in FIGS. 16A and 16B) withpressure or epoxy. Container 202, as a pouch, may also be heat sealed toheat sink 101 with heat seals 231 b and 231 c.

As container 202 is a pouch, it may expand after phase-change material203 changes phase from a first phase to a second phase as a result ofphase-change material 203 having absorb a certain amount of thermalenergy therein. Likewise, container 202 may contract as phase-changematerial 203 change from the second phase back to the first phase as aresult of the thermal energy being released from phase-change material203.

FIG. 17A is a perspective view of a thermal management assembly 5014 foran electronic apparatus and using heat sink 101 and a thermal reservoirin accordance with some embodiments of the present disclosure. FIG. 17Bis a cross-sectional view of thermal management assembly 5014 of FIG.17A along line HH.

Although heat sink 101 is illustrated in FIGS. 17A and 17B, thoseskilled in the art would appreciate that the scope of the presentdisclosure is not limited thereto. For example, other heat sinks such asheat sink 102, heat sink 103, heat sink 104, heat sink 105 or heat sink106 may be utilized in thermal management assembly 5014. Forillustrative purposes heat sink 101 is shown in the example of FIGS. 17Aand 17B.

Thermal reservoir includes a phase-change material 205 and a container204. Phase-change material 205 is contained in a space defined bycontainer 204 and heat sink 101. Phase-change material 205 may include asalt hydrate, an ionic liquid, paraffin, fatty acid, ester, anorganic-organic compound, an organic-inorganic compound, or aninorganic-inorganic compound. Container 204 may be made of silicon,plastic, ceramic or metal. In the example shown in FIGS. 17A and 17B,container 204 is a silicon container made of silicon. The siliconcontainer includes a hollow therein so that when the silicon containeris coupled to heat sink 101 the hollow faces fins 11 of heat sink 101 tocontain fins 11 therein. As shown in FIGS. 17A and 17B, container 204 iscoupled to the first side of heat sink 101 such that fins 11 of heatsink 101 are in direct contact with phase-change material 205. Container204 may be bonded to heat sink 101 at joints 232 a and 232 b with solderor epoxy.

FIG. 18A is a perspective view of yet another thermal managementassembly 5015 for an electronic apparatus and using a heat sink 101 anda thermal reservoir in accordance with some embodiments of the presentdisclosure. FIG. 18B is a cross-sectional view of thermal managementassembly 5015 of FIG. 18A along line JJ.

Although heat sink 101 is illustrated in FIGS. 18A and 18B, thoseskilled in the art would appreciate that the scope of the presentdisclosure is not limited thereto. For example, other heat sinks such asheat sink 102, heat sink 103, heat sink 104, heat sink 105 or heat sink106 may be utilized in thermal management assembly 5015. Forillustrative purposes heat sink 101 is shown in the example of FIGS. 18Aand 18B.

Thermal reservoir includes a phase-change material 214 and a container213. Phase-change material 214 is contained in a space defined bycontainer 213 and heat sink 101. Phase-change material 214 may include asalt hydrate, an ionic liquid, paraffin, fatty acid, ester, anorganic-organic compound, an organic-inorganic compound, or aninorganic-inorganic compound. Container 213 may be made of silicon,plastic, ceramic or metal. Container 213 includes a hollow therein sothat when the container 213 is coupled to heat sink 101 the hollow facesfins 11 of heat sink 101 to contain fins 11 therein. As shown in FIGS.18A and 18B, container 213 is coupled to the first side of heat sink 101such that fins 11 of heat sink 101 are in direct contact withphase-change material 214. Alternatively, container 213 may be coupledto the second side of heat sink 101 such that ribs 12 of heat sink 101are in direct contact with phase-change material 214.

Thermal management assembly 5015 also includes a heat-generating device212. One side of heat-generating device 212 that faces heat sink 101 ispatterned to receive, accommodate, fit or otherwise engage with heatsink 101. For example, as shown in FIGS. 18A and 18B, heat-generatingdevice 212 may include a number of grooves to interlockingly receive orengage with fins 11 of heat sink 101. Alternatively, the grooves ofheat-generating device 212 may be configured to interlockingly receiveor engage with ribs 12 of heat sink 101. This feature maximizes thesurface area for paths of heat transfer to conduct heat fromheat-generating device 212 to heat sink 101. Medium 215 may be disposedbetween heat sink 101 and heat-generating device 212. Medium 215 may be,for example, thermal paste, thermal epoxy or solder.

FIG. 19A is a perspective view of a part of an electronic apparatus 5016utilizing a thermal management scheme in accordance with someembodiments of the present disclosure. FIG. 19B is a cross-sectionalview of the part of the electronic apparatus 5016 of FIG. 19A along lineKK.

Electronic apparatus 5016 includes a thermal management assembly. Thethermal management assembly may be any of the ones described above or avariation thereof. For example, electronic apparatus 5016 may includethermal management assembly 5001, 5002, 5003, 5004, 5005, 5011, 5012,5013, 5014 or 5015. The thermal management assembly of electronicapparatus 5016 include a thermal management unit which includes one ormore heat sinks. Each of the one or more heat sinks of the thermalmanagement assembly of electronic apparatus 5016 may be any of thepreviously described heat sinks such as, for example, heat sink 101,heat sink 102, heat sink 103, heat sink 104, heat sink 105 or heat sink106. For illustrative purposes heat sink 101 is shown in the example ofFIGS. 19A and 19B.

Electronic apparatus 5016 also includes an enclosure 216 that enclosesthe thermal management assembly therein. Enclosure 216 may be made ofplastic or metal. The metal may be, for example, aluminum. As shown inFIGS. 19A and 19B, an inner side of enclosure 216 that faces the thermalmanagement assembly is configured to interlockingly engage withprotrusions (e.g., the first protrusion structure or the secondprotrusion structure) of the heat sink. This feature allows the firstprotrusion structure of the heat sink to interlock with enclosure 216.For example, the inner side of enclosure 216 that faces the thermalmanagement assembly may include multiple grooves recessed into the innerside of enclosure 216 and corresponding to fins 11 of heat sink 101 ofthe thermal management assembly such that the grooves of enclosure 216and fins 11 of heat sink 101 engage in an interlocking fashion.Alternatively, the inner side of enclosure 216 that faces the thermalmanagement assembly may include multiple ribs 219 protruding from theinner side of enclosure 216 and corresponding to fins 11 of heat sink101 of the thermal management assembly such that the ribs of enclosure216 and fins 11 of heat sink 101 engage in an interlocking fashion. Inthe example shown in FIGS. 19A and 19B, ribs 219 on the inner side ofenclosure 216 interlock with fins 11 of heat sink 101.

In some other embodiments (not shown), the inner side of enclosure 216that faces the thermal management assembly may include multiple groovesrecessed into the inner side of enclosure 216 and corresponding to ribs12 of heat sink 101 of the thermal management assembly such that thegrooves of enclosure 216 and ribs 12 of heat sink 101 engage in aninterlocking fashion. Alternatively, the inner side of enclosure 216that faces the thermal management assembly may include multiple ribs 219protruding from the inner side of enclosure 216 and corresponding toribs 12 of heat sink 101 of the thermal management assembly such thatthe ribs of enclosure 216 and ribs 12 of heat sink 101 engage in aninterlocking fashion.

This feature maximizes the surface area for paths of heat transfer toconduct heat between enclosure 216 and heat sink 101. Medium 215 may bedisposed between heat sink 101 and heat-generating device 212. Medium215 may be, for example, thermal paste, thermal epoxy or solder.

When one or more heat-generating devices are thermally coupled to theheat sink, whether directly or indirectly, at least a portion of theheat transferred to the heat sink may be dissipated to enclosure 216through protrusions (e.g., fins or ribs) of the heat sink that interlockwith the grooves or ribs of enclosure 216. In this case, enclosure 216functions as a thermal ground for the heat sink. The one or moreheat-generating devices may be mounted with thermal epoxy (e.g., whenthe one or more heat-generating devices include a microprocessor orgraphics chip), thermal epoxy (e.g., to aid the removal of heat fromelectronic apparatus 5016) or solder (e.g., when the one or moreheat-generating devices include a LED or VCSEL).

Alternatively, as shown in FIGS. 19A and 19B, a thermal reservoir may becoupled to one side of the heat sink while the other side of the heatsink is coupled to enclosure 216. The thermal reservoir may includecontainer 213. Container 213 may be made of silicon, plastic, ceramic ormetal. Container 213 contains phase-change material 214 therein forprotrusions (e.g., ribs 12 as shown in FIGS. 19A and 19B) of the heatsink (e.g., heat sink 101) to be in direct contact with phase-changematerial 214. In this case, heat in enclosure 216 may be transferred tophase-change material 214 of the thermal reservoir through the heatsink. Advantageously, when electronic apparatus 5016 is a portabledevice such as a smartphone, enclosure 216 would not be hot or even warmto touch as at least a portion of the thermal energy in enclosure 216 istransferred to the thermal reservoir through the heat sink. For example,during operation of electronic apparatus 5016, thermal energy insideenclosure 216 (e.g., transferred to enclosure 216 by one or morecontacts between enclosure 216 and the one or more heat-generatingdevices of electronic apparatus 5016) may be transferred to and absorbedby phase-change material 214 due to temperature difference, i.e.,thermal gradient, between enclosure 216 and thermal reservoir in whichphase-change material 214 is contained. When electronic apparatus 5016is not in operation or is in a sleep mode, standby mode or a type oflow-power mode, thermal energy may be released from phase-changematerial 214 to enclosure 216 due to a reversal in temperature gradient(e.g., due to more thermal energy in thermal reservoir than in enclosure216). This feature helps avoid temperature rise in enclosure 216 andthus improves the user experience.

ADDITIONAL NOTES AND CONCLUSION

The herein-described subject matter sometimes illustrates differentcomponents contained within, or connected with, different othercomponents. It is to be understood that such depicted architectures aremerely examples, and that in fact many other architectures can beimplemented which achieve the same functionality. In a conceptual sense,any arrangement of components to achieve the same functionality iseffectively “associated” such that the desired functionality isachieved. Hence, any two components herein combined to achieve aparticular functionality can be seen as “associated with” each othersuch that the desired functionality is achieved, irrespective ofarchitectures or intermedial components. Likewise, any two components soassociated can also be viewed as being “operably connected”, or“operably coupled”, to each other to achieve the desired functionality,and any two components capable of being so associated can also be viewedas being “operably couplable”, to each other to achieve the desiredfunctionality. Specific examples of operably couplable include but arenot limited to physically mateable and/or physically interactingcomponents and/or wirelessly interactable and/or wirelessly interactingcomponents and/or logically interacting and/or logically interactablecomponents.

Further, with respect to the use of substantially any plural and/orsingular terms herein, those having skill in the art can translate fromthe plural to the singular and/or from the singular to the plural as isappropriate to the context and/or application. The varioussingular/plural permutations may be expressly set forth herein for sakeof clarity.

It will be understood by those within the art that, in general, termsused herein, and especially in the appended claims, e.g., bodies of theappended claims, are generally intended as “open” terms, e.g., the term“including” should be interpreted as “including but not limited to,” theterm “having” should be interpreted as “having at least,” the term“includes” should be interpreted as “includes but is not limited to,”etc. It will be further understood by those within the art that if aspecific number of an introduced claim recitation is intended, such anintent will be explicitly recited in the claim, and in the absence ofsuch recitation no such intent is present. For example, as an aid tounderstanding, the following appended claims may contain usage of theintroductory phrases “at least one” and “one or more” to introduce claimrecitations. However, the use of such phrases should not be construed toimply that the introduction of a claim recitation by the indefinitearticles “a” or “an” limits any particular claim containing suchintroduced claim recitation to embodiments containing only one suchrecitation, even when the same claim includes the introductory phrases“one or more” or “at least one” and indefinite articles such as “a” or“an,” e.g., “a” and/or “an” should be interpreted to mean “at least one”or “one or more;” the same holds true for the use of definite articlesused to introduce claim recitations. In addition, even if a specificnumber of an introduced claim recitation is explicitly recited, thoseskilled in the art will recognize that such recitation should beinterpreted to mean at least the recited number, e.g., the barerecitation of “two recitations,” without other modifiers, means at leasttwo recitations, or two or more recitations. Furthermore, in thoseinstances where a convention analogous to “at least one of A, B, and C,etc.” is used, in general such a construction is intended in the senseone having skill in the art would understand the convention, e.g., “asystem having at least one of A, B, and C” would include but not belimited to systems that have A alone, B alone, C alone, A and Btogether, A and C together, B and C together, and/or A, B, and Ctogether, etc. In those instances where a convention analogous to “atleast one of A, B, or C, etc.” is used, in general such a constructionis intended in the sense one having skill in the art would understandthe convention, e.g., “a system having at least one of A, B, or C” wouldinclude but not be limited to systems that have A alone, B alone, Calone, A and B together, A and C together, B and C together, and/or A,B, and C together, etc. It will be further understood by those withinthe art that virtually any disjunctive word and/or phrase presenting twoor more alternative terms, whether in the description, claims, ordrawings, should be understood to contemplate the possibilities ofincluding one of the terms, either of the terms, or both terms. Forexample, the phrase “A or B” will be understood to include thepossibilities of “A” or “B” or “A and B.”

From the foregoing, it will be appreciated that various embodiments ofthe present disclosure have been described herein for purposes ofillustration, and that various modifications may be made withoutdeparting from the scope and spirit of the present disclosure.Accordingly, the various embodiments disclosed herein are not intendedto be limiting, with the true scope and spirit being indicated by thefollowing claims.

What is claimed is:
 1. An electronic apparatus, comprising: a main unit,comprising: a substrate having a first side and a second side oppositethe first side, and at least one heat-generating device disposed on thesecond side of the substrate; and a thermal management unit disposed onthe first side of the substrate, the thermal management unit comprisinga heat sink that comprises: a base portion having a first side and asecond side opposite the first side; a first protrusion structureprotruding from the first side of the base portion, the first protrusionstructure comprising a plurality of fins; and a second protrusionstructure protruding from the second side of the base portion, thesecond protrusion structure comprising a plurality of ribs, the secondprotrusion structure in direct contact with the first side of thesubstrate when the heat sink is disposed on the first side of thesubstrate such that at least a portion of heat in the substrate isconducted to the heat sink through the second protrusion structure,wherein the first side of the substrate comprises a pattern configuredto accommodate the plurality of ribs to interlockingly engage with thesecond protrusion structure of the heat sink when the heat sink isdisposed on the first side of the substrate.
 2. The electronic apparatusof claim 1, wherein an amount of protrusion of a first rib of theplurality of ribs measured from the second side of the base portion andan amount of protrusion of a second rib of the plurality of ribsmeasured from the second side of the base portion are different.
 3. Theelectronic apparatus of claim 1, wherein the heat sink is made ofsilicon.
 4. The electronic apparatus of claim 1, wherein the patterncomprises a plurality of grooves corresponding to the ribs of the heatsink, the grooves configured to receive and be in direct contact withthe ribs when the heat sink is disposed on the first side of thesubstrate.
 5. The electronic apparatus of claim 1, wherein the substratecomprises a multi-layered printed circuit board (PCB) comprising aplurality of PCB layers and one or more metal layers each of whichsandwiched between two immediately adjacent PCB layers of the pluralityof PCB layers.
 6. The electronic apparatus of claim 5, wherein one ormore of the PCB layers are patterned to interlockingly engage with thesecond protrusion structure of the heat sink.
 7. The electronicapparatus of claim 6, wherein a surface of each of the one or more ofthe PCB layers that are patterned to interlockingly engage with thesecond protrusion structure of the heat sink defines the first side ofthe substrate and is metalized with a respective metal layer.
 8. Theelectronic apparatus of claim 5, wherein the substrate further comprisesone or more thermal vias traversing a thickness of the substrate fromthe first side of the substrate to the second side of the substrate. 9.The electronic apparatus of claim 8, wherein at least one of the one ormore thermal vias corresponds to a respective one of the at least oneheat-generating device and is configured to conduct heat from therespective one of the at least one heat-generating device in a directionfrom the second side of the substrate toward the first side of thesubstrate.
 10. The electronic apparatus of claim 1, further comprising:an enclosure enclosing the main unit and the thermal management unittherein, an inner side of the enclosure that faces the thermalmanagement unit is configured to interlockingly engage with the firstprotrusion structure of the heat sink.
 11. The electronic apparatus ofclaim 10, wherein the enclosure is made of metal.
 12. An electronicapparatus, comprising: a main unit, comprising: a substrate having afirst side and a second side opposite the first side, and at least oneheat-generating device disposed on the second side of the substrate; anda thermal management unit disposed on the first side of the substrate,the thermal management unit comprising a heat sink that comprises: abase portion having a first side and a second side opposite the firstside; a first protrusion structure protruding from the first side of thebase portion, the first protrusion structure comprising a plurality offins; a second protrusion structure protruding from the second side ofthe base portion, the second protrusion structure comprising a pluralityof ribs, the second protrusion structure in direct contact with thefirst side of the substrate when the heat sink is disposed on the firstside of the substrate such that at least a portion of heat in thesubstrate is conducted to the heat sink through the second protrusionstructure; a phase-change material in direct contact with at least aportion of the heat sink; and a container coupled to the heat sink suchthat the phase-change material is contained in a space defined by thecontainer and the heat sink.
 13. The electronic apparatus of claim 12,wherein the phase-change material comprises a salt hydrate, an ionicliquid, paraffin, fatty acid, ester, an organic-organic compound, anorganic-inorganic compound, or an inorganic-inorganic compound.
 14. Theelectronic apparatus of claim 12, wherein the container is made ofsilicon, plastic, ceramic or metal.
 15. The electronic apparatus ofclaim 12, wherein the container comprises a silicon cover with a hollowtherein.
 16. The electronic apparatus of claim 12, wherein the containercomprises a pouch that is coupled to the heat sink by heat and pressure,solder, pressure-sensitive adhesive, or epoxy.
 17. The electronicapparatus of claim 12, wherein the container comprises a pouch thatincludes a metallic foil.
 18. The electronic apparatus of claim 12,wherein the container comprises a pouch that includes an aluminum foilhaving surface areas coated with biaxially-oriented polyethyleneterephthalate (BoPET).
 19. The electronic apparatus of claim 12, whereinthe container is coupled to the first side of the heat sink such thatthe fins of the heat sink are in direct contact with the phase-changematerial.